Material handing apparatus

ABSTRACT

Material handling apparatus of the conveyor type especially suited for computer controlled operation. Mechanical features and electronic control features including safety precautions are described in a printed circuit processing application.

United States Patent [72] inventors Lewis L. McAlllster Marion;

Harry M. Penman, Cedar Rapids, Iowa; James P. Wiles, Richardson, Tex.

Mar. 23, 1970 Oct. 12, 1971 Collins Radio Company Dallas, Tel.

[2]] Appl. No. [22] Filed [45] Patented [73] Assignee [54] MATERIALHANDING APPARATUS 8 Claims, 15 Drawing Figs.

[52] US. Cl. 198/19, 246/122, 214/86 [5 1] Int. Cl. B231 5/22 [50] FieldotSearch i98/l9;

[56] Relerenoes ciua UNITED STATES PATENTS 3,335,839 8/1967 Neumann198/19 2,535,162 12/1950 Rodgers 246/122 R Primary Eiaminer-Richard E.Aegelter Assistant Examiner'-H. S. Lane Attorneysl-lenry K. Woodward andRobert J. Crawford ABSTRACT: Material handling apparatus of the conveyortype especially suited for computer controlled operation. Mechanicalfeatures and electronic control features including safety precautionsare described in a printed circuit processing application.

PATENTED [1m 1 2 IHYI SHEET 0 1 [IF uvvsnrons. HARRY u. PASSMAN LEWIS L.McALLISTER JAMES P. w! ES BY z KW ATTORNEY PATENTEUUBHZLQYI 3.612.243

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PATENTED DEHZBH PATENTEU our 1 2 |97| SHEET D6 UF INVENTORS.

HARRY M. PASSMAN LEWIS L. McALL/STER JAMES P. WILES ATTORNEYPATENTEUUETIZIQYI 3.612.243

SHEET D70! 11 INVENTORS. HARRY M. PASSMAN LEWIS L. McALL/STER JAMES P.WILES zr mz ATTORNEY PATENTEUUCH2I97I 3.812.243

SHEET USUF 11 I" l 265 S COMMANO A Doc REGISTER f f COMPARATOR D/A A 276l T 270 r 290 POSITION A i 2 I REGISTER I I IMESSENGER INPOSITION L i jlELEVATOR PROXIMITY 286 CONTROL RESYNC COMPARATOR I \288 284 TO ToELEVATOR- MESSENGER CONTROLS CONT OLs FROM B POSITION REGISTER F l G. ll

ELEV NO 294 DOWN LOAD 296 mm MOLOR 304 TRAVEL 204 MESSENGER A 302COMMAND r1 ELEV. LOAD 300 FIG. l2

INVENTOR$ HARRY H. PASS MAN LEWIS L. McALLISTER JAMES P. WILES ATTORNEYPATENTEU DU 1 2 I97! SHEET 1 1 [IF wOaZ mmuE m mwooma 4 U044. z xmOz, mmu mmuE PASSMAN "CALL/3 TER JAMES P. WILES BY A TTORNEY MATERIAL HANDINGAPPARATUS This invention relates generally to material handlingapparatus, and more particularly to material handling apparatus of theconveyor type which is especially suited for computer controlledoperation. One example use of such apparatus is in the processing ofprinted electronic circuits, and the invention will be described withrespect to this application. However, it

. is to be appreciated that other material handling applications arefeasible and within the scope of the invention.

In the processing of printed circuit boards, blanks or unprocessedboards undergo a number of chemicalprocessing steps including cleaning,electrolysis copper deposition, photoresist masking, copper, tin andtin-lead electroplating titnating, resist stripping, and other chemicaletching to define desired circuit patterns. The process readily lendsitself to a continuous process flow with conveyor means for facilitatingtransfer of boards from one process station to the next process station.

Several plating conveyors have been suggested and/or manufactured, butall known systems have structural disadvantages and do not lendthemselves to automatic, computer control.

An object of the present invention is an improved material handlingapparatus of the conveyor type.

Another object of the invention is improved material handling apparatuswhich is adaptable to the process of printed electronic circuits.

Still another object of the invention is improved material handlingapparatus which is suited for computed controlled operation.

Yet another object of the invention is a printed circuit productionsystem including conveyor means which may be automatically, computercontrolled. 7

Another object of the invention is improved material handling apparatusfor printed electronic circuit fabrication which is flexible inoperation and which has no structural parts other than board supportmeans moving over process tanks.

Briefly, in a printed circuit processing application the presentinvention includes a plurality of process tanks in a sequentially spacedarrangement, board support means, each tank having an opening forreceiving said board support means, each board support means including alift member extending beyond the periphery of a process tank when thesupport means is positioned within the tank. A rail support and travelsystem is provided with each line of tanks, and one or more lateraltransfer means, or messengers, including elevator means for removing orinserting board support means into and out of each tank is providedwhich travels on the rail support system. The drive means and controlmeans for the messengers is designed to allow either a manual test orcomputer control mode of operation.

The invention and objects and features thereof will be more fullyunderstood from the following detailed description and appended claimswhen taken with the drawings, in which:

FIG. 1 is a top view of a conveyor system in accordance with the presentinvention;

FIG. 2 is a side view of the conveyor system of FIG. 1;

FIG. 3 is a side view of a messenger taken along the line of lateralmovement of a messenger;

FIG. 4 is a side view of the support means for the messenger cable forpower and logic circuits;

FIG. 5 is a section view of the support means in FIG. 4 includingmoveable cable support members;

FIG. 6 is an isometric view of the messenger and elevator means;

FIG. 7 is an isometric view of a messenger, work support means, and loadand unload stations;

FIG. 8 is an isometric view of a process tank, agitator and messenger;

FIG. 9 is an isometric view of the messenger drive means and encoder;

FIG. 10. is a functional block diagram of the messenger control system;

FIG. I l is a functional block diagram of the controller portion of themessenger control system of FIG. 10;

FIG. 12 is a schematic of the messenger control relays;

FIG. 13 is a schematic of elevator control relays;

FIG. 14 is a schematic of controller address means of each elevator; and

FIG. 15 is a schematic of work station clamp control relays.

Referring now to the drawings, FIG. I is a top view of a conveyor systemin accordance with the present invention adapted for the production ofprinted circuit boards. A plurality of processing tanks 10 are seriallyarranged for carrying out the rinsing, plating and etching stepsinprinted circuit fabrication. A walkway I2 is provided along one sideof the tanks for human operators, and a horizontal rail assembly 14comprising two parallel, vertically spaced rails is provided along theother side of the tanks. Two lateral transfer messen gers l6 and 18 areprovided which travel along horizontal rail 14 for transferringworkpieces between the various process tanks. Only one such messenger isnecessary in the conveyor system, however, a preferred embodimentincludes two such messengers which may operate along the railsimultaneously. Various safety features are incorporated to preventcollisions, as will be described further below.

Referring again to the tanks I0, it will be noted that at either end ofthe tank, support means 20 is provided for receiving a work supportmember (not shown in this view). Reciprocating pneumatic cylinders 22are activated upon receipt of a work support assembly to provideagitation of workpieces within each tank during a processing operation.The agitator assembly will be further described below with reference toFIG. 8. At one end ofthe line of tanks a load station 24 and an unloadstation 26 are provided for loading and unloading the work supportassemblies. I r

The messengers 16 and 18 are provided with elevators 28 which lower andraise workpieces into and out of the process tanks. The elevators travelalong a vertical rail assembly comprising a pair of vertical rails 30which are a part of the messenger. Arms 32 extend from either end ofmessenger I6 for initiating a safety brake and absorbing impact shouldthe mes senger be involved in a collision due to control means failure.

FIG. 2 is a side view of the conveyor system shown in FIG. I and furtherillustrates the agitator support assembly 29 of the tanks 10, the loadand unload stations 24 and 26, respectively, and the messengers l6 and18. It will further be notedthat the horizontal travel rail assemblyincludes an upper rail and a lower rail, both designated l4, along whichthe messengers travel. As will be described further below, the elevators28 for each messenger may assume one of three positions, namely a lowerunloaded position as assumed by the elevator of messenger 18, an upperloaded position as assumed by the elevator of messenger l6, and anintermediate position at which the workpieces are loaded and unloaded.Control means to be described further below allows a messenger to movealong the horizontal travel rails I4 only when the messenger elevator isunloaded and in the lower position or loaded and in the upper position.

The two messengers are driven independently by cable drive meansincluding servo-controlled motors 34 and 36 located at one end of theconveyor line. An encoder 37 is provided which senses the movement ofthe drive cables and thereby indicates digitally the movement andposition of the messengers. The servo-controlled motors and encoder willbe further described below with reference to FIG. 9 and the controlsystem shown in FIG. 10.

FIG. 3 is a side section view taken along the axis of the lateral railassembly and further illustrates the relationship of the messenger and aprocess tank. fire walkway 12 is on one side of tank 10 and themessenger 16 and horizontal travel rails 14 are on the opposite side ofthe tank. The agitator support 20 is piyotally mounted to permit lateralmovement when activated by reciprocating pneumatic cylinder.

An upper messenger housing 38 includesbearings for riding an upper 'raill4 and further includes brake means for use in emergency stops. Thelower rail 14 is engaged by the mes senger in a manner to support themessenger assembly upright and counteract the movement force when theelevator 28 is supporting a load. Movement of elevator 28 along rail 30is provided by means of cable 40 and drive means 42, which are furtherdescribed below.

Power to the elevator drive motor 42 is provided by means of cable 44.Cable 44 is accommodated by support 46 so that the cable may be extendedas the messenger moves along the rail assembly 14 thereby maintainingpower to the elevator drive 40. The support 46, as further illustratedin FIG. 4, includes a channel 48 having a bottom opening which issupported in spaced relationship with respect to member 50 by means of abracket 52. Member 50 is mounted to support member 54 for upper rail 14and bottom support member 56.

FIG. is a section view of channel 48 and illustrates cable supportcarriers 58 which include rollers 60 which provide movement for thecarriers 58 along the channel 48. Thus, as a messenger moves along therail assembly, cable 44 for the elevator drive is extended by means ofthe cable carrier 58 movement along channel 48.

FIG. 6 is an isometric view which further illustrates details of themessenger, elevator and rail assemblies. As the messenger 16 moves alongupper rail 14, photoelectric detector means within upper messengerhousing 38 senses pins 60 which are provided along the rail assembly,and the electrical pulse is transmitted to the messenger control systemto resync the indicated messenger position. These resync signals arenecessary to correct possible errors from cable driven encoder 37. Cable62 is associated with tank position sensing means and transmits anin-position signal to the controller when a messenger arrives at thetank position. Cables 64 and 66 which provide movement of the messengersalong rail assembly 14 also drive the encoder 37 as described above withreference to FIG. 2.

As described above, elevator 28 may assume one of three positions as itmoves along vertical rails 30, namely a lower unloaded position (asshown in FIG. 6), an upper loaded position (not shown in FIG. 6), and anintermediate position for receiving or discharging a load. At each oneof these positions a microswitch is provided to generate a signalindicative of the elevator being at the respective position. Microswitch68 is shown for indicating the intermediate position at which loads arereceived and discharged by the elevator. Importance of these positionindicating switches will be appreciated from the description of themessenger control system, below.

Elevator 28 is driven by means of cable 44 and a drive motor withinhousing 42. As described above with reference to FIGS. 3-5, the elevatordrive motor receives its power through cable 44 which is supported bychannel 48.

The load receiving portion of elevator 28 is shown in a partiallycutaway view and includes an upper pair of rollers 70 and a lower pairof rollers 72 which receive a pin member of the work support means,described below with reference to FIG. 7. When the pin member is inposition within elevator 28, microswitch 74 is tripped and aload-in-position message is transmitted to the messenger control system.

FIG. 7 is an isometric view of a work holder 80 including a plurality ofprinted circuit boards 82 arranged and supported thereby to facilitatechemical processing. The work holder 80 is shown in the unload position26 with the load position 24 adjacent thereto. Associated with load andunload positions 24 and 26 are microswitches 84 and 86, respectively,which are actuated when a work holder is in position in the load orunload stations. Associated with each tank or work station is amicroswitch similar to switches 84 and 86 which indicates the presenceof a work holder in the tank. Extending downwardly from work holder 80is a rod 88 which is received by elevator 28 when the work holder is tobe elevated, as described above with reference to FIG. 6. In this figurethe elevator 28 is shown in the down position ready to receive pin 88and work holder 80 upon raising of the elevator.

An isometric view of a tank 10 and associated agitator means is shown inFIG. 8 along with a work holder 80 supported by elevator 28 andpositioned for insertion into process tank 10. The agitator support 20includes members 100 and 102 at either end of the tank for receiving thework holder 80 as the elevator is lowered. A microswitch is associatedwith member 100 which is tripped upon the positioning of work holder 80in the agitator support and thereby providing a work-in-place signal tothe control means. Agitator support 20 is pivotally mounted as shown at104 and 106 thereby permitting lateral movement of the agitator supportwhen cylinder 22 is actuated. Tank 10 includes an opening 108 in its topsurface for receiving the protruding portion of work holder 80 aselevator 28 is lowered. Connected with elevator 28 is cable which passesover a pulley 110 mounted in the upper elevator structure and is drivenby the elevator drive means 42 (shown in FIG. 6).

The drive means and encoders for the two messengers are shown in FIG. 9.Cables 64 and 66 which are connected to the two messengers are drivenrespectively by servomotors 34 and 36. Power to the two servomotors isprovided by suitable SCR amplifiers such as General Electric's Vl SCRamplifier. Position indication for the two messengers is provided byencoder means 37 which comprises two incremental digital encoders 112and 114 each of which is driven by either cable 64 or cable 66.Commercially available encoders such as the Model 834 optical encodermanufactured by Disc Instruments, Inc. may be utilized for the encoders112 and 114. By mounting a 6.6-inch diameter sheave on the encoder, 200pulses per revolution will result in a pulse for every 0. I056 inch ofcable traveled. Because of slippage and runout problems connected withdriving the encoder from a sheave driver by the drive cable, the indextransducers 60 (shown in FIG. 6) are provided to correct errors inposition by resyncing the position indicator in the control means, asfurther described below.

The control means for the conveyor will now be described with referenceto FIGS. 10-15. Referring to FIG. 10, a functional block diagram of theentire control means is illustrated. In computer operations, programcontrol is effected through the Time Division Multiplexed (TDM) loop tothe input device adapter 200. Device adapter 200 stores incominginstructions and feeds command information in compatible form toposition controller 202 and feeds back information to the computer. Inresponse to command inputs, position controller 202 through messengercommand portions for a messenger "A" and a messenger B," controls theservoamplifiers 204 and 206 which in turn drive "A memenger motor 208and 8" mesenger motor 210, respectively. When driving the twomessengers, mesenger motors 208 and 210 drive A encoder 212 and "B"encoder 214, as described above with reference to FIG. 9, which providemessenger position information through encoder translators 216 and 218back to the position controller 202.

Associated with the rail asembly are die "A" resync transducers 222 andB" resync transducers 224 which provide corrections to the A" messengerand B messenger position registers which may be required due to slippageand runout problems connected with driving the encoders 212 and 214.

Asociated with the position controller 202 is tank selection decodingand comparison means 228 which controls the operations at each workstation tank through means of relay drivers 230 and tank select relays232. Auxiliary control relays 234 provide feedback to the computer loopto indicate when a messenger and a tank processing cycle is completed.The auxiliary relays 234, which provides inputs to the "A elevator motorcontrol 236 and "B" elevator motor control 238, incorporates safetyfeatures for safely controlling A" elevator motor 240 and 8" elevatormotor 242, as described further below with respect to FIGS. 12l5. Levelsensors 244 including microswitches at the three stationary elevatorpositions (lower unloaded position, intermediate load/unload position,and upper loaded position) provide inputs to the elevator controls 236and 238 and auxiliary control 234.

mums mos Position controller 202 is programmed to provide emergencybraking should the indicated A" messenger and 8" messenger positionsapproach each other below a prescribed minimum. In such a situation, theservoamplifiers 204 and 206 are deactuated, armature excitation isremoved from the drive motors, and the resulting generator behavior ofthe motors provides dynamic braking. Additionally, should the messengerapproach each other and arms 32 engage, "A" rail clamp 252 and "B" railclamp 254 are mechanically actuated.

Test panel 256 is provided for a manual mode operation of the conveyorsystem. Inputs to elevator controls 236 and 238, emergency braking 248and 250, position controller 202, and servoamplifiers 204 and 206 areprovided from the test panel 256 to effect the manual mode operation.

Power for the system is provided by a main power supply 258 which maytypically be 460 volts, 3 phase AC for compatibility with theservoamplifiers. Logic power supply 260, typically +5 volts DC, andrelay power supply 262, typically 24 volts DC and encoder power supply263 are provided in cooperation with the main power supply 258.

The A" messenger control portion of the position controller 202 isillustrated within block 265 in FIG. 11. Command inputs from the testmode or computer 264 are fed to a command register 266 in the positioncontroller. In response to the received command, comparator 268 comparesthe command register position with the indicated position A register 270and in response thereto provides an input to the servoampliiier 272through digital-to-analog converter 274. Amplifier 272 energizes "A"messenger motor 276 which in turn drives the messenger to the commandposition. Tachometer 278 provides feedback to the amplifier 272 andthereby governs the motor speed. Motor 276 also drives encoder 282 whichupdates position A" register 270. Also, as above described, resynctransducers 284 function to correct any errors in the position "A"register caused by cable slippage, for example, as the messenger ismoved along the track.

As a safetyfeature proximity comparator 286 is provided to measure therelative proximity of the two messengers and stop messenger operationupon the distance between the two messengers dropping below a prescribedminimum. Inputs are received by proximity comparator 286 from theposition A" register 270 and from the 8" position register, and controlsignals are provided to stop operation of the elevators and themessengers upon the indication of an imminent collision.

Afier a command is received by the position controller and a messengeris moved to the command position, a comparator 268 provides a signal tothe elevator control 288 which, together with a signal from themessenger is position microswitch at the prescribed tank station,commences elevator operation to load or unload at the work station.

To prevent improper and possibly damaging operation of the conveyorsystem, a number of safety features are incorporated in the auxiliarycontrol relays to insure safe operation of the messengers and elevators.

FIG. 12 is the relay portion which controls the messenger operation. Acommand to messenger A closes motor A relay contacts 292 for initiatingoperation of servo "A" amplifier 204. However, to complete the circuitto the servoamplifier the elevator down position contacts 294 and the noload indication contacts 296 must be closed, or the elevator up contacts298 and the load in position contacts 300 must be closed as indicated bythe parallel network. That is to say, the messenger cannot be moved itthe elevator is in the load/unload position or is moving between the upand down positions.

Travel of the messenger is permitted only when the elevator is I downand unloaded or up and loaded. Further, relay contacts 302 which arecontrolled by the proximity comparator 286 of FIG. 11 must be closed,brake contacts 304 which are controlled by the messenger brakemust beclosed, overtravel contacts 306 which are located on microswitches ateither end of the rail assembly must be closed, and contacts 308 whichare controlled by the messenger arriving at the command destination mustbe closed. Thus, for the messenger to operate in response to a command,the elevator mustbe down and un loaded or up and loaded, proximitycomparator 286-must indicate a safe distance between messengers, and themessenger brake must not be actuated. Further, should the messengertravel exceed the limit of the rail assembly, overtravel switch 306 isopened thus stopping the messenger, and once the messenger arrives atthe command position relay contacts 308 are opened thus deenergizing themessenger drive. i

The relays for raising and lowering the elevator on messenger A areillustrated in FIG. 13. Power to actuate the raise elevator A" relay 310includes, the parallel network shown generally at 3l2, and power toactuate the lower elevator A" relay 314 includes a parallel networkshown generally at 316. Referring first to the raise elevator circuitry,an elevator overtravel relay 318 is normally closed but is opened uponthe elevator overtravelling either the upper position or the lowerposition. Power to the raise relay" 310 is provided through theovertravel switch 318 and through one of the three legs of parallelnetwork 310. The upper leg is for test mode operation and includes amanually operated relay 320 which is serially connected with test moderelay 322. Automatic mode operation of the elevator is provided by themiddle and lower legs of the parallel network 312. The middlev legincludes relay 324 which is closed when theworkpiece supported by thetank agitator assembly is unclamped and thus ready to be raised.Serially connected with relay 324 is relay 326 which is closed when nolower command is present (thereby preventing conflicting commandsignals), lower position relay 328 is closed when the elevator isin thelower position, relay 330 is closed when the messenger is in position atthe proper work station, and relay 332 is closed when automatic modeoperation is desired.

Should the messenger be at the load station and a raisecommand isreceived, a load station relay 334 is provided which shunts theunclamped relay 324 since load stations do not have clamps. Once theelevator begins moving upward it will be noted that the center leg isopened by the lower position relay contact 328 opening. In order tocontinue the raising of the messenger to the upper position the bottomleg further includes a bar in place relay contacts 336 which normally!is closed but opens should the elevator move past the intermediatepickup position and the load support means fail to actuate switch 74(see FIG. 6). Serially connected with contacts 336 are bypass relay 338which is opened upon movement of the elevator and proximity switch 340which is normally closed but opens upon receiving a warning from theproximity comparator 286, shown in FIG. 11.

In series with the parallel circuit 3l2 is a relay 342 which opens uponthe elevator assuming the upper positionand a safety interlock 344 whichcooperatively functions with a safety interlock relay 346 in the lowercommand circuit to prevent relays 210 and 214 from being simultaneouslyenergized.

The lower elevator command relay circuit including parallel circuit 316is very similar to the above-described circuit for the raise command.The lower elevator relay 314 is energized through overtravel contacts318, through, the-parallel network 316, through relay contacts 348.which opens upon the elevator assuming the lower position, and interlockrelay contacts 346. Again, the parallel network 316 includes three legsincluding an upper leg having a manually operated relay 350 which isserially connected with manual mode operation relay contacts 352. Thecenter leg includes relay contacts 354 which indicate that the clampsolenoid is deenergized, contacts 355 which indicate that no raisecommand has been received, relay contacts 356 which are closed. with theelevator in the upper position, relay contacts 358'which are closed whenthe messenger is in the proper work'position, and the automatic modeoperation contacts 360. Shunting contacts'354 are unload positioncontacts 361. The bottomleg comprises bypass relay contacts 362 whichare closed upon the lowering of elevator "A" and provides a bypass tothe'icenter leg which relay contacts 356 open. Serially connected withbypass relay contacts 362 are proximity comparator control relaycontacts 364 which stop operation of the elevator upon receipt of acommand from proximity comparator 286, shown in FIG. I 1.

When the elevator assumes either the upper or lower positions, a timedelay relay 370 momentarily closes thereby initiating a send messagesignal which is generated by the circuit shown in FIG. 14. The timedelay relay 370 is energized through upper position relay contacts 372or lower position relay contacts 374 which are closed upon the elevatorassuming the upper position or lower position.

Referring to FIG. 14, the computer is advised that the previous commandhas been completed by means of the time delay relays actuated by theelevator assuming either the upper or lower position, indicated at 370,or a similar time delay relay 376 upon the messenger moving to a parkposition at either end of the mesenger travel tracks. Thus, when eitherthe elevators move to the upper or lower positions, or the messengermoves to a park position, time delay relays are momentarily closedthereby sending a next command signal back to the computer.

The relay controlling the clamp at each work station are illustrated inFIG. 15. As above described with reference to FIG. 13, the elevatormotor is disabled when the clamp at the work station is activated andholding a work support means in position within the tank. Thus, in orderto allow the elevator to function at a particular work station, theclamp solenoid relay 380 must be deenergized. Clamp 380 is energizedwhenever a workpiece is in place thereby closing relay contacts 382 andneither messenger A nor messenger B are at the work station as indicatedby the position controller thereby opening relay contacts 384 or 386, ora process at the particular work station is in progress thereby closingrelay contacts 388, or a messenger is not in position at the particularwork station as indicated by the messenger sensing means at each workstation thereby rendering relay contacts 390 closed. Thus, in order fora messenger to pick up a workpiece at the particular work station, theprocess at the work station must be completed, and a messenger must beat the selected tank location as indicated by the position controllerand by the messenger sensing means at the work station.

An operation cycle for the messenger is as follows:

1. Receive command.

2. Move empty with elevator in lower position to the programmed tankposition.

3. Raise elevator, engage work support rack and elevate to upperposition.

4. Request next command.

5. Receive command.

6. Move loaded to programmed tank position.

7. Lower elevator, deposit work support rack in the tank.

8. Lower elevator to down position.

9. Request next command.

A specification summary of one embodiment of the conveyor system inaccordance withthe above description is as follows:

Number of Tanks-30 Distance Between Tank Centerlines-IlOiir inches(nonaccumulative) Park Stationsrone/messenger; at opposite endsLoad/Unload Station-One Each at Same End Messenger Weight-300 poundsmaximum including work load Messenger Support-Ball Bearing on 2-inchDiameter Rail DriveDirect Cable Drive Horizontal PositioningAccuracy-10.250 inch Horizontal Transfer Acceleration/Deceleration5.33

feet/sec. (constant) Horizontal Transfer Velocityl feet/sec. maximumHorizontal Drive Cable Sizelfi-inch Diameter (7X19) s.s.

Horizontal Drive Sheave-9-inch Diameter Horizontal DriveMotor-Servo-controlled Horizontal Messenger Travell,052 inches, Park Ato Park B Horizontal Messenger Braking-Dynamic plus Mechanical BrakingHorizontal Position Sensing-Incremental Encoder While the invention hasbeen described with reference to a specific embodiment and application,the description is illustrative and is not to be construed as limitingthe scope of the invention. Various modifications and changes may occurto those skilled in the art without departing from the spirit and scopeof the invention.

We claim:

l. A conveyor system especially suited for computer controlled operationcomprising:

a. a plurality of work stations,

b. work receiving means associated with each work station,

c. a horizontal rail means spaced from and aligned with said pluralityof work stations,

d. at least one messenger means movable along said horizontal rail meansfor transporting work means between work stations,

c. said messenger means including elevator means for depositing orremoving work means at said work stations and vertical rail means alongwhich said elevator means travels,

f. drive means for said messenger means and for said elevator means, and

g. control means for selectively moving said messenger means to workstations and removing or depositing work means at said work stationsincluding position register means and digital encoder means associatedwith said drive means for cooperatively indicating the position of saidmessenger means, and resync transducer means associated with saidhorizontal rail means for correcting errors in said position registermeans as said messenger means moves along said horizontal track.

2. A conveyor system as definedby claim I wherein said plurality of workstations are process tanks and said work means includes printed circuitsand a work support means.

3. A conveyor system as defined by claim 1 wherein said work supportmeans includes a vertical depending member which is supportably receivedby said elevator means.

4. A conveyor system as defined by claim 1 and including two messengermeans movable along said horizontal rail means.

5. A conveyor system as defined by claim 4 wherein said control meansincludes comparator means for comparing indicated positions of said twomessenger means and generating signal in response to said indicatedpositions approaching each other below a minimum limit,-said drive meansfor said mes senger means and for said elevator means being responsiveto said signal and stopping movement of said messenger means and saidelevator means.

6. A conveyor system as defined by claim 1 wherein said control meansincludes switch means associated with each work station for indicatingthe presence of a messenger and the completion of a process operation,switch means associated with each work receiving means for indicatingthe presence of a work support means, switch means associated with saidelevator means for indicating an upper elevator position and a lowerelevator position, and for indicating the presence of work support meansin said elevator means.

7. A conveyor system as defined by claim 6 wherein said control meansfurther includes means for permitting messenger movement along saidhorizontal rail means only where said elevator means is in said upperposition and loaded or is in said lower position and unloaded.

8. A conveyor system as defined by claim 7 and including two messengermeans movable along said horizontal rail means.

1. A conveyor system especially suited for computer controlled operationcomprising: a. a plurality of work stations, b. work receiving meansassociated with each work station, c. a horizontal rail means spacedfrom and aligned with said plurality of work stations, d. at least onemessenger means movable along said horizontal rail means fortransporting work means between work stations, e. said messenger meansincluding elevator means for depositing or removing work means at saidwork stations and vertical rail means along which said elevator meanstravels, f. drive means for said messenger means and for said elevatormeans, and g. control means for selectively moving said messenger meansto work stations and removing or depositing work means at said workstations including position register means and digital encoder meansassociated with said drive means for cooperatively indicating theposition of said messenger means, and resync transducer means associatedwith said horizontal rail means for correcting errors in said positionregister means as said messenger means moves along said horizontaltrack.
 2. A conveyor system as defined by claim 1 wherein said pluralityof work stations are process tanks and said work means iNcludes printedcircuits and a work support means.
 3. A conveyor system as defined byclaim 1 wherein said work support means includes a vertical dependingmember which is supportably received by said elevator means.
 4. Aconveyor system as defined by claim 1 and including two messenger meansmovable along said horizontal rail means.
 5. A conveyor system asdefined by claim 4 wherein said control means includes comparator meansfor comparing indicated positions of said two messenger means andgenerating signal in response to said indicated positions approachingeach other below a minimum limit, said drive means for said messengermeans and for said elevator means being responsive to said signal andstopping movement of said messenger means and said elevator means.
 6. Aconveyor system as defined by claim 1 wherein said control meansincludes switch means associated with each work station for indicatingthe presence of a messenger and the completion of a process operation,switch means associated with each work receiving means for indicatingthe presence of a work support means, switch means associated with saidelevator means for indicating an upper elevator position and a lowerelevator position, and for indicating the presence of work support meansin said elevator means.
 7. A conveyor system as defined by claim 6wherein said control means further includes means for permittingmessenger movement along said horizontal rail means only where saidelevator means is in said upper position and loaded or is in said lowerposition and unloaded.
 8. A conveyor system as defined by claim 7 andincluding two messenger means movable along said horizontal rail means.